of the Vicinity of Duhlin. 381 



from about one-fourth to nne-tenlh of an inch in 

 thickness, and further divisible into pieced of a rhom- 

 buidal form, of various angles. 



The surface of the concretions is smooth, and strongly 

 ^listening. 



Th'e mineral, in fragments, is slightly translucent on the 

 edacs : 



It scratches glass, but is easily scratched by quartz : 



It is easily broken : 



Specific gravity 2"29. 



Before the blowpipe v^ithout addition it yields a greyish- 

 white frothy enamel. 



It is in some places porphyrilic ; containing imbedded 

 minute crystals of felspar and of quartz. 



A letter from a very intelligent observer, who has ex- 

 amined this substance in its rfative place, states the fol- 

 lowing particulars respecting its position and geological 

 relations; viz. "The vein is^tlrst observable in the Town- 

 land of Newry, at the bottom of a bank of granite, about 

 half a mile from the northern end of the town, on the 

 right of the road leading to Downpatrick : it crosses the 

 road, and runs due westward, ending on the side of the 

 great road from Newry to Belfast. Its length, so far as 

 hitherto observed, is half a mile." 



" The rock, which is covered with mould to the depth 

 of about a foot, consists of grey granite : the vein is about 

 two feet and a 4ialf, or two and a quarter in width ; at the 

 places of contact both the granite and pitchstone are dis- 

 integrated, the latter being almost as soft as clay, but be- 

 coming gradually harder as" it approaches the centre of the 

 vein, 'fhe structure of the vein is foliated, the folia being 

 perpendicular to the horizon, and also to the walls; and 

 besides these, there are seams that run longitudinally, pa- 

 rallel to the horizon, and nearly perpendicular to the folia." 



Although the substance above described presents some 

 peculiarity, in being divisible into rhomboidal fragments, 

 it approaches in this respect to the pitchstone of Arran 

 "in lamellar concretions;" a variety considered by Mr. 

 Jameson as having hitherto occurred only in that island *, 

 and which holds, as it were, a middle place, between the 

 mineral from Newry and that possessing the more common 

 characters. The occurrence of pitchstone in geological 

 circumstances like those above mentioned, has hitherto 

 been very rare ; but Mr. Jameson has described a vein of 



• Jameson's Mineralogy, vol. !■ p- 2G1. 



Bb3 it 



